WASHINGTON--President Obama discloses his best fund-raisers. The leading Republican 2012 presidential contenders refuse to reveal the names of their major fund-raisers, even though the last two GOP White House nominees--John McCain in 2008 and George Bush in 2004--released the names of their "bundlers."

Obama will take some heat as the media and other groups--non-partisan and partisan--put his bundlers under a microscope. The other candidates are keeping secret their bundlers. Why the need to disclose? Because to know the whole story when it comes to raising political cash--you have to know the names of the bundlers.

A big loophole in how federal contributions are reported to the Federal Election Commission means the public has to rely almost entirely on voluntary disclosure. A bundler is a well-connected person who uses his or her personal network to raise money for a candidate. A bundler is especially important in federal contests, where individuals face donation caps of $2,500 for a primary and $2,500 for a general election.

This is not a partisan matter. People who follow my work know that for years I have pushed Republicans and Democrats to disclose bundlers and campaign fund-raising events. I was on Obama's back about disclosure when he was running to be a senator from Illinois in 2004. In the 2008 presidential contest, Obama was the first to disclose his bundlers, starting in 2007.

After Obama released his bundler list last week--some 244 folks who raised at least $50,000-ABC News and the Huffington Post called GOP campaigns to ask if they will disclose. None said yes.

Just as Obama did, the 2012 GOP presidential candidates need to come around.

"What do they have to hide?" Gabriela Schneider, the communications director for the non-partisan watchdog Sunlight Foundation told me.

On Wednesday, Democratic National Committee Chair Rep. Debbie Wasserman Schultz (D-Fl.) wrote to Republican National Committee Chair Reince Priebus challenging him to prod GOP candidates to disclose their bundlers.

Reported Devin Dwyer at ABC News:
"Former Massachusetts Gov. Mitt Romney, who disclosed all the names of his bundlers during the 2008 primary campaign, will only now reveal the identities of five registered lobbyist-bundlers who helped him net $18 million in the second quarter.

"We disclose all of the information about our donors as required by law, and anyone who is interested can review it publicly," Romney campaign spokeswoman Andrea Saul said in a statement."
Reported Sam Stein with Paul Blumenthal at Huffington Post:
"We are following the FEC's disclosure rules to their fullest extent," said Alex Conant, a spokesperson for former Minnesota Governor Tim Pawlenty's presidential campaign.

"Tim Miller, a spokesperson for Jon Huntsman's campaign, confirmed that the former Utah Governor and ex-U.S. Ambassador to China would not be releasing bundlers' names."